With recent advancement in electronics industry, there has been rapid increase in demand for silicon-based thin films used for the production of semiconductors, such as polycrystalline silicon thin films or amorphous silicon thin films. These days, the importance of monosilane (SiH4) and higher silanes (SinH2n+2; n is an integer of 2 or more) such as disilane (Si2H6) have been increasing as raw materials used to produce those silicon-based thin films used for the production of semiconductors. The demand for disilane, in particular, is expected to significantly increase as a raw material of silicon-based thin films used for the production of microfabricated latest semiconductors.
Hitherto known processes for producing a higher silane such as disilane include:
(1) a production process utilizing hydrogen reduction of silicon using hydrogen sulfide or a metal sulfide as a catalyst (Patent Literature 1); (2) a production process utilizing the reduction of a silicon chloride compound (Patent Literature 2); (3) a production process utilizing the reaction between a silicon oxide having a silicon-hydrogen bond or a silicon-silicon bond, and a hydride, an alkoxide or an amalgam of an alkali metal or an alkali earth metal, (Patent Literature 3); (4) a production process utilizing the decomposition of magnesium silicide with an acid (Patent Literature 4); (5) a production process utilizing the discharge in a monosilane gas (Patent Literature 5); and (6) a production process utilizing the condensation of monosilane using a transition metal complex as a catalyst (Patent Literature 6).
Production processes are also reported in which a lower silane is subjected to, for example, thermal treatment in order to be converted to a higher silane (Patent Literatures 7, 8 and 9). In these techniques, for example, monosilane is thermally treated at 350 to 550° C. to produce a higher silane.
In another known production process, thermal treatment is carried out with the use of a catalyst which is alumina, a composite oxide containing alumina, or an alumina containing a noble metal element such as palladium and rhenium; in which technique, disilane is produced from monosilane at a temperature as low as about 300° C. (Patent Literature 10).
In the production of the silicon-based thin films used for materials like semiconductors, there is continuing demand for technology that fulfills not just economic efficiency but also allows for stable and efficient production on an industrial scale.